1910] on the Chemical Significance of Crystal Structure. 833 



priated by the constituent atoms are, in any one member, directly 

 proportional to the valency numbers of the corresponding elements. 



Another set of observations of a very convincing character, 

 although of a totally different kind, is laid out in Table IV. 



Table IV. — Molecular Volumes op the Noemal Paeafpins 

 AT THEiE Melting Points. 



Mean value of S = 2-970. 



Experimental determinations of the molecular volumes of a long 

 series of normal paraffins, made on the Hquid substances at tempera- 

 tures at which the materials are in physically similar conditions, 

 are stated in column 4. Since the valency of carbon is four 

 times that of hydrogen it would be anticipated from the crystallo- 

 graphic conclusions previously drawn, that each carbon atom should 

 appropriate four times as large a space for occupation as one hydrogen 

 atom ; the quotient of the molecular volume by the valency sum or 

 valency volume, W, should consequently lead to the same value, S, 

 in the case of all the hydrocarbons. The mean value of S, namely, 

 the atomic volume of hydrogen, is thus calculated as '2 ' 970, and that 

 it is constant within very narrow limits is seen on comparing columns 

 4 and 5, the latter of which states the product of the valency volume, 

 W, by the value 2*970. The simple relation between the atomic 

 volumes of carbon and hydrogen in the liquid normal paraffins indi- 

 cated in the above table was recently pointed out by Lebas, and is 



3 I 2 



